CHAPTER 1 Intro to Biology The Microbial World

Biology is the scientific study of life. The Scope of Life –Life is structured on a size scale ranging from the molecular to the global.

Biologists explore life at many levels Life at Its Many Levels

Seven traits common to all living things. The Unity of Life

Cells and Their DNA The cell is the lowest level of structure that can perform all activities required for life. We can distinguish two major types of cells: –Prokaryotic Simple, small, no membrane-bound organelles –Eukaryotic Larger, more complex, contains organelles. The nucleus is the largest organelle in most eukaryotic cells.

Figure 1.5

All cells use DNA as the chemical material of genes. –Genes are the units of inheritance The language of DNA contains just four letters: –A, G, C, T

Life in Its Diverse Forms Diversity is the hallmark of life. –Scientists have identified and named 1.8 million species. –Estimates of the total diversity range from 10 million to over 200 million species.

The Three Domains of Life The three domains of life are: –Bacteria –Archaea –Eukarya

Bacteria and Archaea are both prokaryotic domains.

Figure Domain Eukarya includes four kingdoms: –Plantae –Fungi** –Animalia –Protists**

Unity in the Diversity of Life Underlying the diversity of life is a striking unity, especially at the lower levels of structure. –Example: the universal genetic language of DNA Biological evolution accounts for this combination of unity and diversity.

Evolution: Biology’s Unifying Theme The evolutionary view of life came into focus in 1859 when Charles Darwin published The Origin of Species.

Darwin’s book developed two main points: –Descent with modification –Natural selection

Natural Selection Diversity observed on the Galápagos Islands. He thought of adaptation to the environment and the origin of new species as closely related processes. Darwin synthesized the theory of natural selection from two observations that were neither profound nor original. –Fact 1: Overproduction and competition –Fact 2: Individual variation

Darwin’s Inescapable Conclusion The inescapable conclusion: Unequal reproductive success –It is this unequal reproductive success that Darwin called natural selection. –The product of natural selection is adaptation. Natural selection is the mechanism of evolution.

Figure 1.14

Observing Natural Selection There are many examples of natural selection in action. –The development of antibiotic-resistant bacteria is one.

Microbiology The study of microscopic organisms. –Includes bacteria, archaea, viruses, protists and fungi. Why study microbes???

Why Study Microbes??? They are, by far, the most abundant organisms on earth. Profound effects on human populations –How do you think microbes effect YOUR life?

Agricultural Implications Fermentation & digestion in the gut of cows, our source of beef & milk Bacillus thuringiensis as a pesticide Salmonella in chicks – Preempt (microbial spray w/ 29 organisms) now being used.

Plant Pathogens Plant pathogens that can destroy entire crops of plants in one growing season… –Bitter rot – Anthracnose of apple caused by Colletotrichum gloeosporoides But can also be beneficial –Botrytis cinerea

Plant Pathogens (Cont)

Industrial & Food Plants Production of lactic and acetic acids Fungi produces citric acid for soda Bacteria produce yogurt and sour cream Wine, beer & bread depend on yeasts (fungi) Other fungi produce Roquefort and Stilton Cheeses. Mushrooms are the most commonly thought of edible fungus, available in a huge variety.

Technological & Environmental Applications Many pharmaceuticals are produced by bacteria and fungi (ie Penicillin) Some microbes can be used as biocontrol agents B. thuringiensis genes inserted into plants oil eating bacteria fungi that attack insects like –Cordyceps

The Roots of Microbiology Anton van Leeuwenhoek –Skilled at lens grinding, lenses 200x more powerful. Published first known descriptions of bacteria Louis Pasteur –Microbes may be agents of infectious disease. Showed that yeast cells were responsible for wine fermentation. –Proposed the “germ theory of disease”: microbes play a significant role in infectious disease. –Led to Pasteurization of many products today, ended the idea of spontaneous generation.

The Roots of Microbiology Robert Koch –Grew bacteria on solid culture medium –Studied anthrax in sheep, those studies led to the first proof of the germ theory of disease –Koch’s methods are still used today and are knowne as “Koch’s Postulates”

The Microbial World Bacteria Prokaryotes (simple, single-celled organisms) Existed for 3.5 billion years on earth Occupy all niches on earth Some are heterotrophs and some are autotrophs Some are aerobic and some are anaerobic Some are beneficial to humans, but many are involved in disease.

The Microbial World Protozoa Single-celled eukaryotes Share many similarities with certain human cells, so they have been useful in research Many are free-living heterotrophs, but some are both heterotrophic and autotrophic Algae are photosynthetic, nonheterotrophic protists. Some are multicellular (seaweeds) and others are unicellular (making them microbes) Unicellular algae cause huge losses in fisheries during alga blooms. Red tides, for example.

The Microbial World Fungi Major decomposers on earth External digestion, then absorption of nutrients across their cells. (other microbes do not feed this way) Many are multicellular, but single-celled fungi are known as yeasts Many are important animal & plant pathogens

The Microbial World Viruses Not living Nucleic acid fragment with protein coat Reproduce only in the host